1. Field of the Invention
The present invention relates to a method of manufacturing a head of an inkjet printer, and more particularly, to a method of manufacturing a head of an inkjet printer and forming a nozzle on a nozzle plate using a laser beam radiated on the nozzle plate through an ink passage of a substrate.
2. Description of the Related Art
Generally, inkjet printers are categorized into a bubble-jet type, a Mach type, a thermal type and a thermal compression type according to ways of discharging ink. The bubble-jet type printer ejects ink droplets by means of bubbles generated by a heating element heating liquid ink. The bubble-jet type printer includes a head having a nozzle plate formed at one side of an ink chamber wall of the head. The nozzle plate has a nozzle formed therein, and the ink chamber wall defines a space that serves as an ink chamber. Formed at opposite sides of the ink chamber wall are a heater and a plate. The heater is positioned in the ink chamber, and the plate has an ink feeding passage communicating with the ink chamber.
Recently, demands for an inkjet printer having a higher resolution and speed have increased, and in an attempt to satisfy the demands, manufacturers have been focused on ways to reduce the diameter of nozzles, increase the density of the nozzles and also the accuracy of the nozzles in terms of form and position. In one example of such heads of inkjet printers that have been developed and commercialized, the nozzle of the nozzle plate is tapered, i.e., the nozzle having a smaller diameter in an outside portion than an inside portion which is closer to the ink chamber, so that the ink is discharged through the nozzle more efficiently at the higher speed and with the higher resolution.
Generally, the head of the inkjet printer, which has the tapered nozzle as described above, is made through a process of forming the nozzle in the nozzle plate in a tapered pattern, and then attaching the nozzle plate to the substrate on which the heater is formed.
However, the above-described method has a problem. That is, since the nozzle plate is attached to the heater-formed substrate after the nozzle is formed in the nozzle plate, it is very difficult to increase the positional accuracy of the nozzle. Because of the low positional accuracy of the nozzle, when the nozzle, the ink chamber and/or the ink feeding passage of the ink chamber are not aligned with each other accurately, the orientation of the ink droplets is deviated when the ink droplets are ejected through the nozzle, and as a result, a printing image could not have a desirable resolution.
Another suggestion to solve the above-described problem is that the nozzle plate be attached to the heater-formed substrate before the nozzle is formed in the nozzle plate.
Although the nozzle, the ink chamber and/or the ink feeding passage of the substrate are aligned easily, this method also has a problem. That is, since the nozzle is formed in the nozzle plate after the nozzle plate is attached to the heater-formed substrate, the alignment of the heater on the substrate and the nozzle of the nozzle plate becomes difficult.
Also, according to the another suggestion, since the nozzle is formed after the nozzle plate is attached to the substrate, and since the nozzle has to be formed by radiating the laser beam from the outside of the nozzle plate toward the ink chamber, it is very difficult to form the nozzle in the tapered pattern, i.e., it is hard to form the nozzle to be narrowing in diameter from the inside portion to the outside portion (i.e., the nozzle narrow from the ink chamber to an outside of the nozzle plate), which is needed for the efficient discharge of the ink. Although the nozzle plate is subject to the laser beam with uniform width, since the outside portion of the nozzle plate receives the laser beam earlier, the outside portion of the nozzle plate absorbs more energy and thus is formed to be larger in diameter than other portions of the nozzle plate. In order to solve this problem, some suggestions have been made about the ways to form the nozzle in the tapered pattern, i.e., the nozzle to be narrowing from the inside portion to the outside portion.
FIG. 1 is a cross-sectional view showing a method of making a nozzle structure for the efficient discharge of the ink by varying an incident angle of a laser beam. As shown in FIG. 1, formed on a substrate 1 are a heater 2 and an ink chamber wall 4. The ink chamber wall 4 has a predetermined height for providing an ink chamber 3. A nozzle plate 5 is attached to the ink chamber wall 4. In a state that the substrate 1, the ink chamber wall 4 and the nozzle plate 5 are attached to each other, the laser beam is radiated to a certain location of the nozzle plate 5, which is designated to to form the nozzle 6. In order to obtain a nozzle of desirable structure, at least one laser beam is radiated from at least three different directions A, B, C at different incident angles. Here, in order to vary the incident angle, a plurality of laser beams are used, or the nozzle plate mechanically moves so as to vary the incident angle of the laser beam that is incident on the nozzle plate 5. However, it is difficult to align a plurality of laser beams to focus on the same nozzle formed area. It is also difficult to align the nozzle plate with respect to the laser beam by mechanically moving the nozzle plate, and accordingly, it is difficult to obtain the desirable nozzle structure for the efficient discharge of the ink, while the productivity deteriorates considerably due to a complicated manufacturing process.
FIG. 2 shows another method of forming the nozzle 6. In this example, the nozzle 6 is formed using laser beams having different shapes. The shape of a laser beam varies by an optical system 7, and a laser beam having the variable shape is radiated on the nozzle formed area to form the nozzle 6. In this method, the most important thing is to accurately focus the laser beam on the correct location of the nozzle plate. Accordingly, it is hard to obtain the desirable nozzle structure for the efficient discharge of the ink, and a considerable deterioration of productivity is unavoidable due to the complicated manufacturing process. A reference numeral 8 in FIGS. 1 and 2 is an ink feeding passage.